Jupiter: discovery of a “strange ball” among the 12 new moons
These moons were observed for the first time in 2017. One of them is “different from all other known Jupiterian moons”.
Twelve new moons were discovered around Jupiter, bringing to 79 the total number of its known satellites, a record among the planets of our solar system, said Tuesday an American team of astronomers. Researcher Scott Sheppard of the Carnegie Institution for Science has described one of these new moons as a “strange ball” because of its small size: Just under one kilometer in diameter, making it “probably the smallest satellite of Jupiter. Its orbit is also “different from that of all other known Jupiterian moons,” said the astronomer.
It takes about a year and a half for this “strange ball” to circle Jupiter, whose inclined orbit intersects those of a cloud of other moons moving in the opposite direction of the rotation of Jupiter. “It’s an unstable situation,” Scott Sheppard commented. “Frontal collisions can quickly dislocate satellites and reduce them to dust.” The “strange ball”, like two recently discovered moons, turns in the same direction as Jupiter. It takes about a year for the nearest satellites to go around the world, against two years for those more distant. All these moons could be fragments resulting from collisions between larger cosmic bodies.
Astronomers have proposed to call “ the strange ball “Valetudo” , named after the great-granddaughter of the Roman god Jupiter, goddess of health and hygiene. The Italian astronomer Galileo discovered the first four moons of Jupiter in 1610.
The team of astronomers behind the recent discovery was not looking for new Jupiter satellites, but they appeared in the field of their telescopes as they searched for planets beyond Pluto. The new moons were observed for the first time in 2017 for a Chile-based telescope operated by the US National Astronomical Observatory. It took a year to confirm the trajectory of their orbits using several other telescopes in the United States and Chile.
Astronomers have discovered a new “Super-Earth”
Based on the gravitational microlens method, an international team of astronomers announces that it has detected a new “Super-Earth” surrounding a star about five times less massive than our Sun.
Based on the effect of the gravitational lens, the microlens method is primarily used to detect planetary and stellar objects regardless of the light they emit. Therefore, this technique is sensitive to the mass of objects, especially to low-mass planets such as “super-Earths”, extrasolar worlds with a mass greater than that of our planet of origin.
So far, only about 2% of known exoplanets have been discovered by microlenses. When a new object of this type is discovered, an alert to the entire scientific community is issued to allow follow-up observations. The researchers are then interested in events showing signs of disturbances that could be due to the presence of a planet. In this case, the OGLE-2017-BLG-0482 microlens event was detected on April 8, 2017, from the Las Campanas Observatory in Chile. The subsequent analysis of the event by an international team of astronomers has indeed led to the discovery of an anomaly; a planetary signal.
“We reported the discovery of a super-Earth planet orbiting a star of small mass M,” wrote the researchers in the journal arXiv. According to the study, the newly discovered planet, designated OGLE-2017-BLG-0482Lb, is about nine times more massive than the Earth and orbits around its host at a distance of about 1.8 AU (one AU equals Earth-Sun distance, about 150 million kilometers). The planet orbits about 270 million km from its star, about 0.2 solar mass. The newly discovered planetary system is located at about 19,000 from the microlens event.
In conclusion, the authors emphasize the importance of their discovery, which demonstrates that the microlens is a method to be considered for detecting low-mass planets in orbit around low-mass stars, such as OGLE-2017- BLG-0482Lb.
While the radial velocity method is effective at detecting planets up to 100 light-years from Earth, and transit photometry can detect planets hundreds of light-years away, the microlens can find planets thousands of light-years. It is also the most effective at detecting telluric planets between 1 and 10 astronomical units (AU) of Sun-like stars.
Astronomers may have discovered the very first “exomoon”
Signals captured by the Hubble telescope seem to indicate the presence of a moon-like no other in its vicinity. An “exomoon” whose dimensions would be close to those of Neptune.
After the discovery of thousands of exoplanets, would humans have entered the era of “exomoon”? Possible … But not sure. A new report by a duo of researchers at Columbia University, combining data from Kepler and Hubble telescopes, suggests a Neptune-sized moon orbiting a planet of several thousand light-years from Earth.
The planet in question bears the singing name of Kepler 1625b, and would have a mass far superior to that of the giant Jupiter. It orbits around the 1025-year-old Kepler Star 1625, located in the constellation Cygnus. The distance of the latter from the Earth has been estimated at about 7,100 light-years in 2017.
An abnormal transit detected
It is by taking an interest in this planet and its star that the researchers have highlighted the signing of a transit with strange anomalies. “We saw small deviations and flickering in the light curve that caught our attention,” says David Kipping in a NASA statement. Anomalies that the researchers confirmed by continuing their observations.
If the discovery of this new moon is confirmed, it could challenge previous assumptions about the size that these satellites can take.
According to them, two theories could explain the phenomenon: it could be due to the existence of a second planet in the Kepler 1625 system or to that of a moon. The problem is that Kepler has not yet detected any second planet, suggesting that the second theory would be more credible. “A companion moon is the simplest and most natural explanation,” says Kipping.
If the discovery of this new moon is confirmed, it could challenge previous assumptions about the size that these satellites can take. Our understanding of the system of formation of planets and their moons is indeed difficult to dissociate from the understanding we have of the appearance of life on Earth and in space.
Questioning of our knowledge
If the models we have based on our knowledge of the Solar System are correct, the number of moons in the universe should far exceed that of the planets. But these offer a field of development of life more propitious than most places in the universe.
Our exomoon seems, by its characteristics, to escape the classic training scenarios.
Therefore, calculating the frequency with which they are formed and understanding the mechanisms of this training plays a crucial role in the search for life undertaken by scientists. However, our exomoon seems, by its characteristics, to escape the classic training scenarios, so far meticulously constructed.
“The existence of this hypothetical star would call to revise the very concept of what a moon,” says René Heller of the Max Planck Institute. “It would have formed in a completely different way from any moon in our solar system.”
Almost too amazing to be true
While the largest moon in our solar system barely reaches half the mass of Mercury, the new candidate would be 10 times more massive than all the terrestrial planets and hundreds of moons of the solar system combined. A giant who sows both emotion and doubt. “This moon would have properties for the least surprising, which is a good reason to exercise our skepticism,” said researcher and co-author David Kipping.
“If it were the 10th known object of this type, we would call it” discovery “without hesitation, but since this is the first one, further examination is required.” More complete data will have to be collected, because although the hypothesis of Kipping and his colleague Teachey remains the most elegant to explain the data collected, it also raises many questions. “It’s time for the scientific community to review our findings,” Kipping concludes.